Lineshape analysis time domain

The complementary method to time-resolved measurements is the spectroscopy in the energy domain. Energy-resolved experiments determine the Fourier transform of the exponential decay in the time domain, which yields a Lorentzian for the intrinsic spectral lineshape. As mentioned in Section 3.2.4, photoemission does not permit to separate inelastic and elastic decay processes, which both contribute to the linewidth. Because the energy resolution of inverse photoemission is usually not sufficient for a lineshape analysis, this section is devoted to photoemission of occupied states, providing an additional complementary aspect to the time-resolved measurements of transiently populated unoccupied states by 2-PPF. Occupied (initial) states can also be observed by 2-PPE spectroscopy. Their linewidth is similar to the values obtained in regular photoemission [107]. 

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